The present invention relates to hinge constructions for plastic molded parts and more particularly to a molded plastic hinge construction for a plastic, blow molded container having a base and a lid connected by the hinge.
Various hinge constructions have been developed for plastic blow molded containers having a lid and a base. One form is referred to as a `live` hinge and is formed by simultaneously molding the lid and base and having a relatively thin webb of material interconnecting the lid and base. With a hinge of this type there can be problems of fatigue and ultimate failure of the webb because of the continuous flexing of the webb.
Another construction utilizes a more conventional type hinge and has a metallic pin inserted through interfitting bosses after molding. The problem with this latter type of construction is that it requires an extra assembly step after molding and in addition causes alignment problems. Further it is not uncommon for the pins to be inserted out of alignment or with the lid and base out of alignment resulting in a poor fit and an unsightly appearance. This is important where the containers are used to house and display for sale relatively expensive tools. An unsightly container could possibly have a negative effect on the sale of the tools while a well constructed container could have the opposite effect.
In the present invention the hinge is defined by a pin on one member and a depending journal on the other. The members are blow molded and generally are formed from an extruded parison of the plastic material to have a double walled hollow construction with each wall being relatively thin e.g. approximately 0.060 inch. However, in order to provide adequate strength and rigidity the pin and journal are formed by compression of a double thickness of the extruded parison material and are not blown, and hence are solid and not hollow. By molding the pin and journal integrally with their associated members, accurate location of each with their associated members can be provided and proper fit and alignment can be more readily assured between the members. i.e. lid and base. At the same time the members rotate relatively to each other and are not faced with the fatigue problems of the `live hinge` which continuously flexes.
In addition, in the present invention the journal is provided to be at least partially of a strap like, depending structure and hence defines a flexible structure which assists in assembly. Further the opening in the journal is formed by a pair of offset semicircular portions whereby forming is facilitated.
Also in the present invention the components of the hinge are compression molded by plastically deforming the material of the parison into a desired shape different from that generally defined by the parison.
Therefore, it is an object of the present invention to provide an improved molded plastic hinge for blow molded containers.
It is another object of the present invention to provide a plastic hinge integrally molded with associated blow molded parts with the hinge being non-blown and formed from compression of a double thickness of the extruded parison.
It is another general object to provide an improved plastic container and hinge of the above described type.